It may just be a lingering impression from the days of prohibition, but the reputation of home-brewing beer for many is that the people who do it are half-way to being militia-men who hide out on communes in places so far off the map that no GPS system will ever find them. Although a lot is being done to address this, the fact is that people are usually prepared to spend more money drinking the pre-made beers than they are to take the time and effort to set up their own home brewing station.
Of course, the initial impression of those who home-brew their own beer is not the only reason why people don’t do it. Some people are quite skilled in brewing while others are not, just as some people are excellent cooks and some people after years of trying still cannot boil an egg. It is understandable that some will cut out the middleman and buy their beer from a liquor store because their own efforts at brewing would be likely to induce vomiting without needing to be drunk in huge quantities.
However, brewing your own beer is not something you should just reject out of hand. If you give it a try, you might find that you are good at it. And if you are, then there is a world of opportunity there for you. If you have never found that beer that tastes just right, you can experiment with different measures, modalities and timings until you get one that is perfect. It is an acquired skill, but one worth acquiring.